The present invention relates to a process for heating ceramic shaped parts, where the shaped parts are heated inductively to the desired temperature.
A discharge sleeve for the continuous casting of liquid metal or conventional steel is already known from U.S. Pat. No. 3,435,992, where the discharge sleeve is heated inductively prior to bringing it into contact with the liquid metal. The discharge sleeve described in this U.S. patent exhibits an electrically conductive insert in a discharge sleeve molded from a refractory material that is substantially not electrically conductive. The electrically conductive insert, which is made preferably from one graphite piece, can be heated with a current of suitable frequency ranging from 3 to 50 kHz with an induction coil, which encloses the discharge sleeve and is arranged in essence coaxially thereto, where, however, at first only the electrically conductive insert absorbs the induction energy and is thereby heated, thus transferring the generated heat though thermal conduction to the actual discharge sleeve made of the refractory material.
Such a discharge sleeve involves, however, only the use of a separate, electrically conductive insert with variable thickness and variable length in proportion to the discharge sleeve, so that the heat buildup varies widely. In addition, the refractory material is not heated through induction, but only through the conduction of heat from the electrically conductive insert. Therefore, with fast heating thermally induced cracks in the refractory material will be generated.